Alzheimer's disease (AD) is associated with a progressive neurons failure. AD is a major cause of dementia, most often dementia and AD are used interchangeably. In Alzheimer's disease (AD), the progressive loss of cognitive, language and emotional functions occurs. Generally, serious AD patients need more care and require assistance in all respects, such as taking a bath, eating, going to the bathroom, etc. Therefore, there are great impacts on the families of those AD patients in their daily lives. Loss of memory is the most often seen symptom of AD. At the very beginning, the symptoms such as memory loss are often mistakenly thought by the family members of AD patients as “age-related.” But a physician can diagnose the disease with cognitive tests and brain scan. Some known symptoms that seriously affects a person's ability to carry out his/her daily activities include no recognition of a place or direction, loss of memory of recent events, bringing up matters of the past repeatedly, or unable to learn new things. As the disease gets worse, patients often have difficulty in expressing himself/herself or making decisions. Gradually, AD patients may lose the ability to recognize family members and relatives. Some AD patients may suffer confusion, agitation, paranoia, mood swings, language breakdown, and general withdrawal. New studies show that the brain damages of AD patients involve the human vision and sense of space. Thus, an AD patient often has problem in identifying a direction or finding his/her way. AD patients may wander on the streets as they forget their destinations or cannot find their way home. At home, AD patients may gradually lose bodily functions, thus have difficulty in carrying out daily activities by themselves. Other damages to the brain cells of AD patients, e.g., the basal forebrain and hippocampus, may lead to long-term memory loss and confusion. Many AD patients eventually die from the disease, or from other causes related to their lifestyle change such as pneumonia. Generally, AD patients can live 6-8 years, but many AD patients can survive for more than 20 years, putting severe burden on their families and society.
The Food and Drug Administration (FDA) of the United States has approved five pharmaceutical treatments for Alzheimer's disease in clinical use, including the cholinesterase inhibitors such as Tacrine and Donepezil. Cholinesterase is an enzyme that catalyzes the hydrolysis of neurotransmitter acetylcholine (AChE) into choline and acetic acid. Those aforementioned approved pharmaceuticals can inhibit cholinesterase and repress the hydrolysis of neurotransmitter acetylcholine (AChE). Consequently, both Tacrine and Donepezil can be used to increase the AChE content in human brain, which in turn may defer the process of memory-loss, and may allow AD patients to continually carry out their daily activities Importantly, those pharmaceutical treatments are unable to cure Alzheimer's disease, but only relieve certain AD symptoms. Moreover, the aforementioned medications have been proved to carry side effects to AD patients, including nausea, headache, diarrhea, insomnia, pain, illusion and dizziness, etc. Therefore, new method for the prevention and treatment of Alzheimer's disease without noticeable side effects are desperately needed.